1. Field of the Invention
The present invention relates to an improved method for manufacturing an aluminum-based composite plate.
2. Description of the Related Art
Automobile disk brakes have disks which are disposed parallel to tires and sandwiched on both sides by pads to thereby halt the disks by friction. The pads are housed in a caliper along with a piston for operating the pads. The pads are frictional plates each prepared by bonding a friction material (produced by thermoforming and polishing a mixture of fibers, a filler material, a friction adjuster and a binder) to a back plate (back metal). The back plates must be of high strength and lightweight because of heat and the compressive force imposed on them through the pads. Recently, it has become common to use aluminum in automobiles and motorcycles for weight reduction. In particular, use of metal-based composite materials (fiber-reinforced metal-based composite materials (FRMs) or metal matrix composites (MMCs) with aluminum as the base metal (matrix phase) has been increasing.
One known process for manufacturing products by extrusion molding of aluminum-based composite materials is "CYLINDER MANUFACTURING METHOD" disclosed in Japanese Patent Laid-Open Publication No. SHO-59-206154. The steps involved in the disclosed method are as summarized below:
(a) SiC chips are stirred and dispersed in molten aluminum, and the mixture is allowed to solidify. PA1 (b) the solidified product is drawn while heated to about 250.degree. C., to fabricate a pipe. PA1 (c) the pipe is cut into a sleeve shape, fitted into a die casting metal mold and then insertion-cast with an aluminum alloy (JIS-ADC12) to thereby provide a cylinder.
The process described in Japanese Patent Laid-Open Publication No. SHO-59-206154 can be utilized to manufacture back plates used on pads of such disk brakes as described above.
However, since the composite materials manufactured by the disclosed method are obtained by combining SiC chips in molten aluminum, they have high resistance to plastic deformation so that it is not easy to work the composite materials into tubes or plates by extrusion molding. In addition, the interface between the aluminum and SIC is in a simple mechanically bonded state. Therefore, such materials exhibit low elongation and have poor workability, similarly to ordinary composite materials. Consequently, it has been a problem that these composite materials have been difficult to mold when it is attempted to obtain desired shapes by extrusion molding or the like, and that production efficiency has therefore been difficult to increase.
Furthermore, when attempts are made to cut composite materials into predetermined shapes, the composite materials manufactured by the above-described method of manufacture which include a ceramic (SiC) and hence have poor workability by machining such as cutting or polishing, thereby increasing production costs.